In 2006, then-Senator Barack Obama co-sponsored a tough law aimed at protecting the public from an accident or terrorist attack at one of the nation’s chemical plants. Opposed by industry and President George W. Bush’s White House, the bill never made it to the Senate floor. A weak substitute was passed instead, and the dangers remain. President Obama can fix the problem.

In a letter to the president last week, a coalition of more than 100 environmental, public health and labor organizations argued that while Congressional gridlock made passage of new legislation even less likely now, the Environmental Protection Agency, under the Clean Air Act, could impose new safety rules on its own. Last month, Christine Todd Whitman, an administrator of the E.P.A. for Mr. Bush, made the same argument to Lisa Jackson, the E.P.A.’s present administrator.

The current chemical safety law, which consists of a modest amendment to a 2007 appropriations bill, is clearly inadequate. It requires companies to submit broad security plans — covering guards, video surveillance, perimeter fencing — to the Department of Homeland Security, but few have been approved or even fully reviewed. Some 2,400 drinking water and wastewater treatment plants, many of which use highly toxic and explosive chlorine gas, are not covered at all.

One of the biggest weaknesses is that the law fails to push industry toward using safer chemicals and processes — ultimately the surest protection against disaster. A compromise bill passed by the House in 2009 would have required the use of alternatives but only when the Department of Homeland Security determined they were feasible and cost effective. Industry argued that the final decision should be theirs, and the bill died in the Senate.

Industry and its Congressional allies will inevitably make the same arguments again. But the case for protecting the American public is clear. A decade after Sept. 11, 2001, thousands of facilities that use dangerous chemicals are still vulnerable. There needs to be a strong safety regime backed by federal enforcement, and the E.P.A. has the authority to put that in place now.